The research focuses upon the axial distribution of heat and water losses along the airways and extends these inquiries: (1) by assessing the external and physiological factors which modulate airway heat and water conservation; (2) by determining the distribution of airways responses to the cooling or drying stimuli which accompany hyperpnea; and (3) by identifying the mechanisms of those responses. Specific experiments proposed will: (i) quantitate heat and water losses along the airways of intubated sheep, and examine how these exchanges balance with heat and water replenishing sources (the bronchial or pulmonary circulations, or heat/water recovery from exhaled gas) to influence airway wall temperature, hydration, and osmolarity; (ii) localize airway narrowing during hyperpnea-induced bronchoconstriction in guinea pigs by obtaining tantalum oxide bronchograms, and relate these airway responses to local stimuli; and (iii) assess the potential roles of mast cell mediator secretion, vagal efferent reflex, and tachykinin release, in effecting guinea pig hyperpnea-induced bronchoconstriction.